RAM Test

This RAM test runs a write and verify memory check inside your browser. It asks for the amount you choose in 16 MB blocks, measures how fast the memory writes, reads and copies, then writes four patterns over every block (each word's own address, a checkerboard, walking ones and a random sequence) and reads every word back. Any word that comes back different is counted as an error. It is a quick first check on Windows, Mac, Linux, ChromeOS and Android, and the steps below cover the two tools that test all of your RAM: Windows Memory Diagnostic and MemTest86.

How to use this RAM test

1. Save your work and close other heavy tabs and programs.
2. Choose a test size. Sizes above half the memory your browser reports are switched off, so the test cannot starve your system.
3. Choose 3 passes for a normal check, or 10 if you are hunting an error that comes and goes.
4. Press Start memory test and watch the memory map. Squares turn yellow while they are written and checked, green when verified and orange if an error is found.
5. Read the verdict, then press Copy results to keep the numbers. The log lists every error with the bits that flipped.

What the results mean

Speeds from a single browser thread are well below the rated bandwidth of your memory, which counts every channel working at once. Use them to compare runs on the same computer, for example before and after enabling an XMP or EXPO memory profile. Two matching modules in dual channel give twice the theoretical bandwidth of one, and graphics built into the processor rely on that bandwidth too, which the webgpu test shows in its memory bandwidth figure. If the browser refuses part of the size you asked for, the map shows striped squares: that is the browser's limit for one tab, not a fault.

What a browser RAM test cannot check

A browser works in virtual memory. It gets whatever physical memory the system hands it, cannot choose addresses, cannot touch memory used by the system or other programs, and runs with the processor caches on. That means it can miss a faulty cell that happens to sit outside the memory it was given. Treat a clean result here as a good sign, not proof. For proof, use one of the tools below, which run before the system loads and test every address.

How to run Windows Memory Diagnostic

1. Save your work. The test restarts the computer.
2. Press the Windows key, type Windows Memory Diagnostic and open it. You can also press Win + R, type mdsched.exe and press Enter.
3. Choose Restart now and check for problems (recommended).
4. The test runs before Windows starts. To run the Extended test, which takes much longer but finds more, press F1, choose Extended and press F10.
5. When it finishes, Windows starts and shows the result in a notification.
6. If you missed it, open Event Viewer, go to Windows Logs, then System, choose Filter Current Log and pick MemoryDiagnostics-Results as the source. The entry says either that no errors were detected or that hardware errors were detected.

Hardware problems were detected

This message means Windows Memory Diagnostic wrote values to your RAM that did not read back correctly. Work through these steps in order:

1. Turn off any memory overclock. In the BIOS, set the memory profile (XMP on Intel, EXPO or DOCP on AMD) to disabled or Auto and test again. Many errors disappear at standard speed.
2. Reseat the modules. Shut down, unplug the power, take each module out and push it back in until the clips click.
3. Test one module at a time in the slot your motherboard manual recommends for a single module. The module that fails on its own is the faulty one.
4. Update the BIOS, which often fixes memory compatibility, especially on new AMD and Intel platforms.
5. Replace the faulty module. Most memory brands, including Corsair, Kingston and G.Skill, give a lifetime or limited lifetime warranty on desktop modules. Laptop memory soldered to the board needs a repair by the maker.

How to test RAM with MemTest86

MemTest86 is free from PassMark at memtest86.com and boots from a USB stick, so it tests every address with nothing else running.

1. Download the free MemTest86 USB image for Windows and extract the zip.
2. Run imageUSB from the extracted folder, choose your USB stick and write the image. This erases the stick.
3. Restart the computer and open the boot menu, usually with F12, F11, F9 or Esc at startup, and choose the USB stick.
4. Let it run. It completes four passes by default, which can take a few hours with a lot of memory.
5. At the end it shows PASS or FAIL and offers to save an HTML report to the stick. Any error, even one, is a fail.

MemTest86 runs on PCs and Intel Macs. On a Mac with Apple silicon, run Apple Diagnostics instead: shut down, press and hold the power button until the startup options appear, then press Command + D. On Linux, many boot menus include MemTest86+, the open source version, and the memtester command tests memory from a running system.

When the browser test finds errors

An error on this page is serious, because the browser reuses memory that the rest of the system relies on. The likely causes, in order, are an unstable memory overclock or XMP profile, a module that is loose or failing, and an unstable processor memory controller at high memory speeds. Disable the memory profile, run the test again, then confirm with MemTest86. If errors also appear in the cpu stress test with the Mixed workload, the problem is in the memory or the processor's memory controller rather than the processor cores.

RAM stress tests for overclocks

A clean MemTest86 run at standard speed does not prove a memory overclock is stable. For that, people run OCCT's memory test or Prime95 with the Blend setting for an hour or more, often together with the gpu stress test to load the whole system. If you are replacing memory because a laptop feels slow, also check the drive with the ssd speed test, since a slow or full drive causes the same stutters as running out of RAM.

RAM test questions